The present invention relates to the arts of spring coiling and computer numerical control. The present invention finds particular application in computer control of spring coiling operations and is described with particular reference thereto. It is to be appreciated, however, the various aspects of the invention will find application in other coiling apparatus or electronic machine controls.
Present demand for heavy duty springs encompasses a wide variety of spring formats. Broadly speaking, springs can be of constant or variable pitch, or of constant or variable diameter. Depending on the final characteristics of a spring, the spring will behave in markedly different ways when placed into use. Some of the variations in the spring properties are changes in the spring force in varying proportion to the compression applied thereto, or variations in the natural resonant frequency of the spring. The multitude of applications for springs dictates a corresponding wide variety of diameters, thicknesses and pitches.
One machine which has found success in the coil spring forming was the "Gogan Coiler", as described in U.S. Pat. No. 3,000,427 issued Sept. 17, 1961, to Joseph Gogan. In the Gogan Coiler, a pliable bar stock was coiled about a mandrel, guided by a lead screw consisting of a round bar with spiral grooves thereon. While the Gogan Coiler performed effectively, one deficiency was that each type of coil to be manufactured required a dedicated lead screw. In addition to necessitating a wide inventory of lead screws, the operator time associated with changing the lead screws and the machine downtime during a changeover detracted from the Gogan Coiler's efficiency.
One effort to improve upon the Gogan Coiler is described in U.S. Pat. No. 3,470,721, issued Oct. 7, 1969, to Scheublein, et al. Scheublein, et al. substituted a pair of fingers driven by a worm gear for the lead screw of the Gogan machine. The coiler disclosed in Scheublein, et al. attempted to meet the demand for variable pitch springs by providing an integral number of discrete pitch variations without a dedicated lead screw for each spring. While the Scheublein, et al. patent may have had some advantages over the Gogan Coiler, it also had some drawbacks. The friction between the fingers and the bar stock from which the coil was formed, coupled with the narrow length of actual guide afforded by the fingers, created problems in the disclosed device.
Another shortcoming of the Scheublein, et al. coiler was that while it may have formed springs with a plurality of pitches, the pitch variations were discrete, i.e. when a certain point in the spring formation was reached a new pitch instantaneously began. Oftentimes, desired coil properties could only be met with constantly varying pitch.
A demand exists for a wide variety of coil springs. It is commonly desired that the spacing of the coils, the pitch of the coils, and the diameter of the coils be varied within a single spring. Presently, springs in which the pitch of the springs vary continuously over the length of the spring are in demand.
The present invention overcomes the foregoing difficulties and others. It contemplates a spring manufacturing device equal to the task of easily, quickly, and less expensively creating virtually any spring necessitated or desired for a particular application.